No, they really would have to record hundreds of voices.... JUST TO NARROW IT DOWN TO THE ONE THAT THEY LIKE.

If they went with your idea of just having one male and one female (regardless of race), then guess what? They have to audition voice actors, record all of them, then go through and meticulously pick out which one they think is the best.

it is by NO MEANS a simple, easy, or cheap process for anyone involved.

"My frozen dairy-based confectionery attracts all the males of the species to the facilities. They all agree on it's superiority. Indeed, it is superior to yours. I could teach you the finer details but that would require monetary recompense on your part."-The Milkshake Song: Vulcan Edition